Chudan Nakayubi Ipponken is a technique in Kyokushin karate. It translates to 'Middle-Level Middle Finger One-Knuckle Fist.' This technique involves forming a fist where the middle finger is extended slightly forward, creating a single-knuckle striking surface, typically aimed at the opponent's midsection or torso. The term 'Chudan' refers to the middle level, 'Nakayubi' indicates middle finger, and 'Ipponken' denotes one-knuckle fist. It is commonly used for close-range strikes to vulnerable areas such as the solar plexus, ribs, or abdomen.